if u did ur research u would know that muay thai boran is considered a deadly art because it was used by warriors to fend off invaders of there country! also many fighters have died in fights due to the ropes that the fighters would were which would cut open there opponents, also traditional muay boran comes with a berrage off attacks. competition thai fighting is the more water down version of muay thai as there emporer tried to make it so there were less deaths in matchs also implementing the use of gloves instead of ropes!!!!

Muay Thai vs Muay Boran

All martial arts started with military versions and police tatics, look at kung fu, kalri, karate, judo, wrestling, muay boran and many others.
Military was first formed in Mesopotamia about 10,000 years ago. Early versions of all martial arts had to be deadly because other tribes would invade others with the intention to kill.

I don't believe that Boran was so deadly, maybe a long time ago, not now! This is to make Boran so mysterious. Those fighters use to jump up in the air to land an elbow, not gonna happen now.